1. Field of the Invention
The present invention relates, in general, to electrical watthour meters and, specifically, to watthour meter mounting apparatus and, more specifically, to watthour meter socket adapters.
2. Description of the Art
In the electric utility industry, plug-in, socket-type watthour meters are commonly employed to measure electrical power consumption in a residential or commercial building establishment. A cabinet or housing is typically mounted on a outside wall of the residence or building and contains a meter socket having pairs of line and load terminals which are connected to electric power line conductors extending from the utility power network and electric conductors connected to the residential or building establishment power distribution network.
S-type, socket-type, plug-in watthour meters have replaced older A base bottom connected meters which were formed of a single piece housing in which the watthour meter was fixedly mounted along with compression terminals which provided connection to the utility power line conductor and the building load distribution conductors. In an installation involving an A-type bottom connected meter, an A to S socket adapter is used to allow a new S-type watthour meter to be installed. The S or socket type watthour meter has outwardly extending blade terminals which are insertable into jaw contacts mounted in an A to S-type meter socket adapter. Bottom mounted terminals on the socket adapter provide electrical connections between contacts mounted on the socket adapter and the line and load conductors in the meter socket. A sealing ring is mounted about an end mounting flange on the socket adapter and a mating mounting flange on a watthour meter to lockably mount the watthour meter to the socket adapter.
Plug-in socket adapters and socket adapters/extenders, both hereafter referred to simply as socket adapters, are designed with outward extending blade terminals to plug into the meter socket housing jaw contacts. Such socket adapters are employed to convert ringless style sockets to ring style sockets or to extend the mounting position of the jaw terminals in the socket housing outward from the socket housing for mounting various electrical equipment, such as test devices or survey recorders, in the socket housing.
Such socket adapters employ a generally annular base having a shell joined thereto and extending outward from one side of the base. Contacts are mounted in the shell and base. Each contact has a female jaw portion disposed interiorly within the shell and a male blade terminal connected to the female jaw portion and extending outward through the base for a plug-in connection to the terminals in the meter socket housing.
Such socket adapters may be employed in both ring style and ringless style socket housings. In a ring style housing, a raised mounting flange is formed on the front cover of the socket housing to which the peripheral edge of the base of the socket adapter mates and is locked thereto by means of a conventional, annular, lockable sealing ring. In a ringless style socket housing, the peripheral edge flange of the base of the socket adapter is disposed interiorly within the socket housing in close proximity to or engagement with a raised annular portion of the cover surrounding an aperture through which the shell portion of the socket adapter extends. In both ringless and ring style socket housings, a separate sealing ring is mounted about a end mounting flange at the outer end of the shell to lockably mount a watthour meter to the socket adapter.
In both bottom connected A to S type adapters as well as S-type socket extenders/adapters, a surge ground conductor is mounted on the meter mounting flange of the socket adapter to engage a ground tab on the base of the watthour meter when the watthour meter is coupled to the socket adapter. A separate wire conductor is connected to the surge ground conductor and passes through the base of the socket adapter to a ground connection in the meter socket. In other types of socket adapters, a rigid connector strap is connected to the surge ground conductor mounted on the meter mounting flange and extends to the base of the socket adapter where it is connected to the base of the socket adapter by a metal fastener. The fastener extends through the base of the socket adapter housing and serves as a mount for a metal tab. The metal tab is positioned exteriorly of the base of the socket adapter housing as in an S-type meter base and engages a corresponding ground contact or connection in the meter socket when the socket adapter is mounted in the meter socket.
Both types of surge ground circuits effectively ground the internal circuits of a watthour meter to the socket ground. However, watthour meters have a metal cover ring mounted about the periphery of the meter base. The cover ring is engaged by the sealing ring used to fixedly mount the watthour meter to the socket adapter, but is otherwise ungrounded since the socket adapter housing spaces the covering and the sealing ring from the meter socket cover which would normally make ground contact with the sealing ring to provide a safe equipment ground to all exposed metal. When an A base meter is used, the terminal access cover is sealed to the metal housing of the meter and provides a ground to the metal seal and cover. In an A to S meter adapter, this seal is attached to a plastic housing and is not grounded.
Present watthour meter construction utilizes a number of external wires which extend outward from the watthour meter for connection to telephone communication circuits, pulse counters, etc., in the socket housing or in external housings. If the wire is pinched or cut, it may contact the watthour meter cover ring, sealing ring and/or security seal thereby placing a voltage on the meter cover ring, sealing ring, and/or security seal which poses a significant safety problem.
Thus, it would be desirable to devise a means for grounding a watthour meter cover ring, sealing ring and/or security seal when the watthour meter is mounted in a meter socket. It would also be desirable to provide an apparatus which would easily and automatically ground a watthour meter cover ring, sealing ring and/or security seal. Finally, it would be desirable to provide a watthour meter socket adapter which automatically grounds a watthour meter cover ring, sealing ring and/or security seal during mounting of a watthour meter to the socket adapter and the mounting of the socket adapter in a meter socket.